#include <iostream>
using namespace std;
class Solution
{
public:
    int ans[4] = {0, 1, 2, 6};
    int clumsy(int N)
    {
        int res = 0;
        if (N >= 4)
        {
            res = N * (N - 1) / (N - 2) + N - 3;
            N -= 4;
            while (N >= 4)
            {
                res += -N * (N - 1) / (N - 2) + N - 3;
                N -= 4;
            }
            res -= ans[N > 0 ? N : 0];
        }
        else
        {
            res = ans[N > 0 ? N : 0];
        }
        return res;
    }
};
int main(int argc, char const *argv[])
{
    Solution s;
    cout << s.clumsy(1) << endl;
    return 0;
}
